1. Field of the Invention
The present invention relates to an automatic emission device suitable for use as an emission light source, such as a flash unit, which is provided with the function of detecting the kind of light source which illuminates a subject.
2. Description of the Related Art
It has heretofore been known that some cameras have a so-called automatic flash emission function which serves to measure a subject luminance (the luminance of external light), make a comparison between the subject luminance and a predetermined value, and, if the subject luminance is lower than the predetermined value, execute emission of flash light, thereby effecting flash photography.
However, if whether flash light is to be employed is primarily determined on the basis of the comparison between the subject luminance and the predetermined value, the following problems will be encountered.
(i) During photography performed in a photographic environment illuminated with a fluorescent lamp, if it is determined that the subject luminance is not less than the predetermined value, and no flash unit emits light, a photograph will be greenish by the influence of the bright line spectrum of the fluorescent lamp.
(ii) During photography performed in a photographic environment illuminated with tungsten light, even if the subject luminance is less than the predetermined value, it is in many cases possible to obtain an atmospheric photograph of warm color tone by performing photography using no flash unit. In other words, if a flash unit is used in a photographic environment illuminated with tungsten light, the contrast between the subject and the background becomes high and, in many cases, a photograph which utterly differs from the atmosphere of that scene will be obtained.
(iii) An arrangement having the function of making a decision as to whether a light source is a fluorescent lamp or tungsten light, that is, the function of detecting the kind of light source, is previously disclosed in Japanese Laid-Open Patent Application No. Hei 3-163538. However, in the light of the problem (ii), it may be considered to provide a camera which has the aforesaid function so that if a user knows that a light source is tungsten light, the user can perform the operation of disabling a flash unit from emitting flash light. However, not only is such an operation complicated, but also if the user is not skilled in photography to any extent, he will not be able to easily determine whether the emission of the flash unit is to be disabled.